Animating creation of a model?
You could try saving your model at various points that you'd like to show, and then import/link them all into one file, and keyframe their visibilities in that file.


Get all your objects into one file.  Import them if you don't think you'll need revisions.
Select the object you'd like to show first.  Get to frame 1.
Hit the "Eye" icon in the outliner to make the object invisible.  Keyframe that object's visibility.  (Hit "I" on the eye icon in Outliner).
Advance to frame 2, make the object visible again, and keyframe it again.
Advance however many frames you'd like this object to be visible.  Let's say 24 frames.  On frame 24, keyframe the visibility again.  Then on frame 25, turn the visibility off, and keyframe it.
Open up a NLA window, select that object, and press the 'down' arrow to push the action onto the stack.  That just enables the NLA to manipulate actions.
Load up your other objects, and load them into the NLA editor.  Just keyframe your un-keyed objects to get them to show up.
Select another object's track, and from the NLA menu select Add >> Action.  Select the action from the first object you keyed.
Repeat step 8 with the other objects.


Hopefully that makes sense to you.  To see a rough idea of this setup, check this out: http://pasteall.org/blend/40878